Qualification for Safeguards Purposes of UF6 Sampling using Alumina – Results of the Evaluation Campaign of ABACC-Cristallini Method

The procedure currently used to sample material from process lines in uranium enrichment plants consists of collecting the uranium hexafluoride (UF6) in gaseous phase by desublimation inside a metal sampling cylinder cooled with liquid nitrogen or in certain facilities in a fluorothene P-10 tube type. The ABACC-Cristallini method (A-C method) has been proposed to collect the UF6 (gas) by adsorption in alumina (Al2O3) in the form of uranyl fluoride (UO2F2) (solid). This method uses a fluorothene P-10 tube type containing alumina pellets that absorb and hydrolyze UF6 directly during the sampling. This new method has advantages compared to the usual method with less residual material left at the facility and also less constraint related to nuclear material transport regulation. ABACC invited seven international laboratories to participate in a UF6 sampling method evaluation campaign. This campaign involved high accuracy measurement of uranium isotopics sampled as UF6 using two different sampling methods: Adsorption on alumina (A-C method) and a standard direct hydrolysis method. The goal of the campaign was to determine if there is any detectable difference in the isotopic composition of UF6 materials when sampled by the two methods. Four different IRMM UF6 Certified Reference Materials were sampled by each of the methods to create four pairs of samples for analysis. Each sample was contained in a P-10 tube, and required dissolution and sample preparation prior to isotopic analysis. This paper presents the results obtained from seven laboratories which will be used for the technical certification process that ABACC is pursuing for qualification of the UF6 sampling A–C method for uranium isotopic determination. The results will also be the basis of the validation process to confirm that the new method can be used for routine safeguards application at the enrichment plants.JRC.G.II.6-Nuclear Safeguards and Forensic